The following abbreviations are used in the present specification:
CM Connection Management
GERAN GSM-Enhanced Data Rates for Global Evolution
GSM Global System for Mobile communications
MSD Minimum Set of Data
MM Mobility Management
PSAP Public Safety Answering Point
RR Radio Resource
RRC Radio Resource Connection
UE User Equipment
UMTS Universal Mobile Telecommunications Systems
UTRAN UMTS Terrestrial Radio Access Network
There have been proposals for an in-vehicle emergency call service such that if for example a vehicle is involved in a (severe) collision, an emergency call over a wireless network can be made promptly so that, in turn, emergency services can be deployed quickly if necessary. The emergency call can be made or at least initiated manually by a human operator or automatically following detection of the collision by suitable sensors in the vehicle.
In Europe for example, there is currently a proposal from the European Commission for a service of this type, which is referred to as “eCall” and shown schematically in overview in FIG. 1. This service is said to be expected to save hundreds of lives a year because of the rapid deployment of the emergency services and because the exact location of the vehicle 1 can be transmitted by a so-called eCall device which is installed in the vehicle 1. The eCall device of this proposal is a wireless device that can establish an emergency voice call 2 (referred to as “E112”) and transfer a data message 3 (the prescribed minimum set of data or MSD) over the cellular network serviced by a radio mast 4 to a PSAP (Public Safety Answering Point) 5. The MSD 3 can include for example vehicle location information (optionally obtained using the Global Positioning System GPS 6), time stamp, number of passengers, Vehicle Identification Number (VIN), and other relevant accident information. It is expected that the eCall MSD information will be sent either immediately following the establishment of the voice call or at any point later during the voice call. The PSAP 5 is an emergency call centre responsible for answering calls made to an emergency telephone number for police, firefighting and ambulance services, and has telephone operators who are also usually responsible for dispatching these emergency services. It should be noted that such emergency devices, including eCall devices in particular, can be used in other applications and are not limited for use in or associated with vehicles.
In general, a wireless device (or “User Equipment” or UE, such as mobile or cell phones, including so-called “smart phones”, and suitably equipped personal digital assistants, pagers, tablet and laptop computers, etc.) can attempt an emergency call without being registered with and without first attempting to register with a network. In the specific case of an eCall device, the eCall device (or more specifically the Mobility Management or MM layer in the eCall device) can be in the “eCALL INACTIVE” state in which it is not registered to any network (see for example the technical specification of the Third Generation Partnership Project 3GPP TS 24.008 V10.3.0). However, it may be desirable, and may even become mandatory, for the eCall device to support PSAP callback, i.e. the emergency telephone operator can call back after release of the emergency call. In such a case, network registration by the eCall device is required. The current proposal therefore is that the registration must be performed by the eCall device before the call. However, with current procedures and specifications, this can cause the emergency call to be delayed or even to fail to be made successfully at all.